1. Field of the Invention
The present invention relates to a method of fabricating an Organic Light Emitting Diode (OLED) which has a simple fabrication process, and provides high contrast and resolution.
2. Description of the Related Art
In general, Organic Light Emitting Diodes (OLEDs) are composed of a substrate, an anode disposed on the substrate, an EMission Layer (EML) disposed on the anode, and a cathode disposed on the EML. In such OLEDs, when a voltage is supplied between the anode and the cathode, holes and electrons are injected into the EML. The injected holes and electrons are recombined in the EML to create excitons, which transition from an excited state to a ground state and emit light.
To implement full-color OLEDs, the OLEDs have EMLs respectively corresponding to red, green and blue. In this case, however, the EMLs corresponding to red, green and blue have different life spans from one another, so that it is difficult to keep a constant white balance during long-time operation of the OLED.
For this reason, it is necessary to form an EML emitting light of a single color and then form a color filter layer for selecting light corresponding to a predetermined color from the light emitted from the EML or a color conversion layer for converting the light emitted from the EML into light having a predetermined color. For example, an active matrix OLED using an EML emitting white light and a color filter layer formed by photolithography is discussed in U.S. Pat. No. 6,515,418. Also, an active matrix OLED using an EML emitting blue light and a color conversion layer formed by photolithography is discussed in U.S. Pat. No. 6,522,066. However, forming the color filter layer or color conversion layer using a photolithography process requires a repetitive process in which each color filter layer or a color conversion layer is formed on the entire surface of a substrate and then patterned by exposure and development processes. A thermal treatment process is required for removing volatile solvents, etc. included in the layer formed by photolithography. As such, the formation of the color filter layer or color conversion layer by using photolithography has disadvantages of numerous processing steps and long fabrication time.
To solve these problems, an OLED including a color filter layer or a color conversion layer formed by vacuum deposition is discussed in Korean Patent Application No. 2001-0000943. However, the color filter layer or the color conversion layer is formed by independently depositing each layer corresponding to red, green and blue using a metal mask. Thus, it is difficult to obtain high resolution due to difficulty in alignment of the metal mask with a substrate. A large investment in equipment is required because each layer corresponding to red, green and blue is deposited in a separate independent chamber.